Electrical connectors that are currently used for connecting conductor runs of a circuit board to other electrical apparatus, e.g., by way of electrical conductor runs of other circuit boards or a ribbon cable, are generally composed of a plug component and a socket component. Each component comprises a body of dielectric material which carries a multiplicity of conductor elements. When the two components are brought into mating relationship, the conductor elements of the plug component engage respective conductor elements of the socket component.
It has hitherto been conventional to mount electronic devices in so-called dual in-line packages. The dual in-line package, or DIP, has connection pins that are connected to the electronic device and are used for mounting the DIP to a circuit board. In particular, holes are drilled in the board and the pins are fitted in the holes. The physical properties of the board material and the limitations of drilling machines have made it conventional for the holes to be drilled at 1.27 mm (0.050 inch) centers. The spacing between the pins imposes a limit on the number of DIPs that can be accommodated by a circuit board of a given size, and consequently limits the number of connections required between that circuit board and other electrical apparatus.
The demand for connection capacity to a circuit board carrying DIPs can generally be met using connectors having conductor elements at 1.27 mm centers: the number of connections is not so large that the space required for the connector limits to a significant extent the area available for DIPs. However, surface mounted devices do not have connection pins that require drilling of circuit boards, and therefore the connection pads of an SMD can be at less than 1.27 mm centers and it is conventional for the connection pads to be at 0.635 mm (0.025 inch) centers. Proposals have been made to place the pads of SMDs even closer, at 0.58 mm (0.020 inch) centers. Such close spacing of the connection pads means that more SMDs than DIPs can be accommodated by a board of a given size, and therefore the demand for connection capacity is much greater for SMDs than for DIPs. It is in fact being found increasingly that the space required for connectors is limiting the area available for SMDs.
It has been proposed that the conventional plug/socket connector be modified so that the spacing between the conductor elements is reduced, e.g., to 0.635 mm. However, in order to maintain adequate space between the conductor elements, it becomes necessary to reduce the width of the conductor elements, and the conductor elements are then liable to be bent or damaged through handling and bringing the connector components into mating relationship.
U S. Pat. No. 840,537 (Weir) discloses a switchboard composed of a pair of parallel boards, each of which is formed with a square array of apertures. The two arrays are aligned, and each aperture contains a metal ring. The ring of one board is connected to the corresponding ring of the other board by inserting a conductive plug through the rings.
U.S. Pat. No. 3,223,956 (Dufendach et al) discloses an instruction apparatus that is somewhat similar to the switchboard of U.S. Pat. No. 840,537, except that it comprises four boards, and a detent is associated with each set of four aligned apertures for establishing two possible insertion positions of the plug or pin that is fitted in the aligned apertures. The pin comprises a core of dielectric material having four equiangularly spaced longitudinal grooves, and metallic spring contacts fitted in these grooves. In one insertion position of the pin, one pair of spring contacts provides electrical connection between two of the boards, and in the other insertion position the other pair of contacts provides electrical connection between the other two boards.
U.S. Pat. No. 3,246,208 (Lex et al) discloses a programming pin board comprising a group of parallel input strips and a group of parallel output strips. The input strips and output strips carry conductor runs. The two groups of strips are arranged in a criss-cross array, and at each crossing point a connection between an input strip and an output strip may be provided by means of a plug having four prongs. The plug is applied to the input and output strips so that one prong is received in each quadrant defined at the crossing point of the input strip and the output strip. Selected prongs have a conductive coating, while the surface layers of the other prongs are electrically insulating. Thus, the conductor runs that are interconnected at the crossing point depend on which prongs have conductive coatings.
U.S. Pat. No. 3,258,730 (Husband et al) discloses a switch block comprising an encapsulating body of dielectric material in which conductive bars are embedded. Holes pass through the dielectric block and the bars so that terminal pins may be inserted to make selective contact between the bars.
U.S. Pat. No. 3,349,361 (Cartelli) discloses a matrix switch in which each deck comprises a board of dielectric material formed with apertures that are partially aligned with apertures in another board, and metal strips that pass through the apertures. Connection between the decks is provided by inserting a metal pin through two partially aligned apertures so as to contact the strips that cross those apertures.
U.S. Pat. No. 3,396,358 (Ballard et al) discloses a connecting matrix structure in which an elongate pin shank carries a plurality of longitudinally spaced leaf-spring contacts.
British Patent No. 953,225 (Longford) discloses a switching matrix in which the plug is made of dielectric material and has ferrules spaced apart along its length and internally connected to conductors that project from the plug.